/**
 * $Id: mxModelCodec.java,v 1.8 2010-11-23 08:46:41 gaudenz Exp $
 * Copyright (c) 2006-2010, Gaudenz Alder, David Benson
 */
package com.mxgraph.io;

import com.mxgraph.model.mxGraphModel;
import com.mxgraph.model.mxICell;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

import java.util.Map;

/**
 * Codec for mxGraphModels. This class is created and registered
 * dynamically at load time and used implicitly via mxCodec
 * and the mxCodecRegistry.
 */
public class mxModelCodec extends mxObjectCodec {

    /**
     * Constructs a new model codec.
     */
    public mxModelCodec() {
        this(new mxGraphModel());
    }

    /**
     * Constructs a new model codec for the given template.
     */
    public mxModelCodec(Object template) {
        this(template, null, null, null);
    }

    /**
     * Constructs a new model codec for the given arguments.
     */
    public mxModelCodec(Object template, String[] exclude, String[] idrefs,
                        Map<String, String> mapping) {
        super(template, exclude, idrefs, mapping);
    }

    /**
     * Encodes the given mxGraphModel by writing a (flat) XML sequence
     * of cell nodes as produced by the mxCellCodec. The sequence is
     * wrapped-up in a node with the name root.
     */
    protected void encodeObject(mxCodec enc, Object obj, Node node) {
        if (obj instanceof mxGraphModel) {
            Node rootNode = enc.document.createElement("root");
            mxGraphModel model = (mxGraphModel) obj;
            enc.encodeCell((mxICell) model.getRoot(), rootNode, true);
            node.appendChild(rootNode);
        }
    }

    /**
     * Reads the cells into the graph model. All cells are children of the root
     * element in the node.
     */
    public Node beforeDecode(mxCodec dec, Node node, Object into) {
        if (node instanceof Element) {
            Element elt = (Element) node;
            mxGraphModel model = null;

            if (into instanceof mxGraphModel) {
                model = (mxGraphModel) into;
            } else {
                model = new mxGraphModel();
            }

            // Reads the cells into the graph model. All cells
            // are children of the root element in the node.
            Node root = elt.getElementsByTagName("root").item(0);
            mxICell rootCell = null;

            if (root != null) {
                Node tmp = root.getFirstChild();

                while (tmp != null) {
                    mxICell cell = dec.decodeCell(tmp, true);

                    if (cell != null && cell.getParent() == null) {
                        rootCell = cell;
                    }

                    tmp = tmp.getNextSibling();
                }

                root.getParentNode().removeChild(root);
            }

            // Sets the root on the model if one has been decoded
            if (rootCell != null) {
                model.setRoot(rootCell);
            }
        }

        return node;
    }

}
